build.yml: Add a "cmake-linux-latest" job

This job builds abseil-cpp and protobuf from source using Cmake and
tries to build protobuf-c against those dependencies using Cmake.

The "latest" build dependencies are being targeted, currently Ubuntu
22.04, abseil-cpp from the lts_2024_01_16 branch, protobuf from the 27.x
branch. Update as newer versions become available.

This uses Cmake's Ninja generator which should be equivalent to the
legacy makefiles that it generates. The Cmake Ninja generator is useful
primarily because it automatically compiles using the maximum amount
of concurrency and it actually shows you the command that failed by
default.

.github/workflows/build.yml

@@ -120,6 +120,72 @@ jobs:
           make test
           make install
 
+  cmake-linux-latest:
+    runs-on: ubuntu-22.04
+
+    env:
+      LDFLAGS: "-Wl,-rpath=/opt/protobuf-c/lib -Wl,--disable-new-dtags"
+
+    steps:
+      - name: Checkout protobuf-c
+        uses: actions/checkout@v4
+
+      - name: Checkout abseil/abseil-cpp
+        uses: actions/checkout@v4
+        with:
+          repository: abseil/abseil-cpp
+          ref: "lts_2024_01_16"
+          path: abseil-cpp
+
+      - name: Checkout protocolbuffers/protobuf
+        uses: actions/checkout@v4
+        with:
+          repository: protocolbuffers/protobuf
+          ref: "27.x"
+          path: protobuf
+
+      - name: Install ninja
+        run: |
+          sudo pip install ninja
+
+      - name: Build abseil-cpp
+        working-directory: "./abseil-cpp"
+        run: |
+          cmake -B build -G Ninja \
+            --install-prefix /opt/protobuf-c \
+            -DCMAKE_CXX_STANDARD=17 \
+            -DABSL_PROPAGATE_CXX_STD=ON \
+            -DBUILD_SHARED_LIBS=ON \
+          ;
+          ninja -C build
+          sudo ninja -C build install
+
+      - name: Build protobuf
+        working-directory: "./protobuf"
+        run: |
+          cmake -B build -G Ninja \
+            --install-prefix /opt/protobuf-c \
+            -DCMAKE_CXX_STANDARD=17 \
+            -DBUILD_SHARED_LIBS=ON \
+            -Dprotobuf_ABSL_PROVIDER=package \
+            -Dprotobuf_BUILD_TESTS=OFF \
+          ;
+          ninja -C build
+          sudo ninja -C build install
+
+      - name: Build protobuf-c
+        run: |
+          cd build-cmake
+          cmake -B build -G Ninja \
+            --install-prefix /opt/protobuf-c \
+            -DCMAKE_CXX_STANDARD=17 \
+            -DBUILD_SHARED_LIBS=ON \
+            -DBUILD_TESTS=ON \
+          ;
+          ninja -C build
+          ninja -C build test
+          sudo ninja -C build install
+
   cmake-msvc:
     strategy:
       matrix: